Episode 3: Primary Suspect
by Castle Season 9
Summary: Castle's daughter is the primary suspect when her best friend is found murdered. With questions arising as to her innocence and the case removed from the 12th Precinct's jurisdiction, Castle, Beckett and the team have to investigate in secret to fight for Alexis. Season 9, episode 3.
1. Chapter 1

**Primary Suspect**

Season 9, Episode 3

Written by ipreferwestside

 _This is a work of fiction by writers with no professional connection to ABC network's Castle. Recognizable characters are the property of Andrew Marlowe and ABC. Names, places, and incidents are products of the author's imagination or are used fictitiously. Any resemblance to actual persons, living or dead, businesses, companies, events, or locales is entirely coincidental._

* * *

The woman sighed as she trudged down the hall, arms wrapped around bags of groceries. It had been a long night at her graveyard shift, and she just wanted to get inside, put her food away, and crawl into bed. As she approached her door, keys in her hand, she heard faint voices, then the slam of a door towards the end of the hall.

She looked up at the sound of quick footsteps approaching, and was startled to see a figure in a dark sweatshirt, hood obscuring their face. The person didn't acknowledge her, just breezed past, rushed steps carrying them towards the stairs.

Curiosity piqued, she abandoned her efforts to get her key into the lock, and instead went to the apartment at the end of the hall. She knew very little about the young woman who lived there, only her name and that she was a student, from brief exchanges when they would meet in the hall. When she noticed the door open, her brows furrowed and she slowed down, not wanting to disturb the young woman.

"Hello?" she called out quietly, then again louder when there was no response. "Is everything okay?" After a momentary pause at the door, she stepped over the threshold and into the apartment.

Still no response.

Her eyes swept through the small living room; still nothing. "Paige? Are you- oh my God!"

The groceries fell from her arms, landing with a thud, as she raised a hand over her mouth. Her eyes were glued to the scene in the kitchen, to the young woman lying facedown on the floor, a pool of blood growing beneath her.

She didn't even notice a stray apple roll from her discarded bag to rest next to the lifeless body.

* * *

Castle turned from the coffee bar, a mug in each hand, and scanned the busy cafe for his companion. He saw the distinctive red hair in the far corner, and as he approached the table, he noticed she was typing furiously on her phone. "Everything okay?" he asked, setting one mug in front of her.

Alexis scowled at her phone before dropping it into her purse, which she set on her lap. "Yeah, fine." She wrapped her fingers around her mug. "Just...stuff. How was your week?"

Castle raised an eyebrow, but didn't press. They hadn't spoken much in the previous couple weeks; he'd been busy at the precinct and with writing, and Alexis had been caught up with a full start of the school year. "It was good." He launched into a story about their latest case, although not as animated as he typically would be.

Alexis hardly reacted, nodding and asking questions when appropriate. When he asked how her week had been, she paused before responding. "It was fine. Busy." She glanced at her phone once more before standing. "I have to get going. Thanks for the coffee, Dad."

Castle stood to hug his daughter goodbye, sitting back down as she left the cafe, and finished his coffee in silence. He'd seen Alexis quiet, but she'd been a different quiet. Distracted, withdrawn. He stared at her half-empty mug, his finger tracing the rim of his. He wasn't planning on going to the precinct that day, but he didn't want to go home yet. Maybe he'd kill some time, bring Kate lunch in a few hours.

After about an hour of playing Angry Birds, his phone started to buzz, and his wife's face appeared on the screen. He grinned at the picture of her, one he'd caught of her sticking her tongue out at him. "Hey, I was just thinking about you. Are you free for lunch in a bit?"

"I wish. Are you still with Alexis?"

Castle straightened in his seat. "No, she just left. Is everything okay?"

"Yeah." Kate sighed, and Castle could imagine her pinching the bridge of her nose. "Sorry, the nausea's killing me right now."

"Oh, why didn't you call sooner?" He stood and grabbed his bag, swinging it over his shoulder as he made his way to the door. "I'll bring you some tea."

"Thanks, babe, but I have some. Ryan and Espo got a case, though. You want in?"

* * *

The apartment was crawling with uniforms when Castle arrived. He'd rather be at the precinct with his wife, or better yet, taking care of her at home. But she didn't want to be coddled, wouldn't want him just sitting around. He'd bring her some tea later, despite her protest, and a cronut. A cronut always made her feel better.

"Hey, Ryan, what do we have?" he asked when he entered the apartment. His eyes took in the scene in front of him: CSU techs tagging and dusting for fingerprints, stepping around the shattered vase on the floor, a discarded grocery bag with food falling out of it.

"About time you showed up," Ryan teased from his crouch by the body on the floor.

"Funny." Castle stopped well outside the pool of blood, careful not to disturb anything. He nodded his thanks to LT when the man handed him a pair of gloves. "Wanna fill me in? Or are you quitting your day job to become a comedian?"

Esposito interrupted any potential comeback from Ryan. "Neighbor only knew the victim in passing. Apparently, she'd just gotten home when she heard arguing, couldn't make out any words. But someone rushed past her, wearing a hoodie. She doesn't know who it was, didn't see a face."

Castle surveyed the room. "I don't see any pictures out here. Do we know who she is yet?"

"Yeah, her name-"

Castle barely registered Ryan informing him of the young woman's identity; his eyes were focused on the victim's face when Lanie turned her over.

"Paige," he whispered.

Ryan and Esposito shared a look. "You know her?"

Castle nodded, barely aware of his hand moving to his coat pocket. "Paige Galloway, she's Alexis's best friend." He dialed Alexis, but was answered only by the happy welcome of her voicemail. "Hey, it's me. Can you call me when you get this?"

How was he going to tell his daughter that her best friend was dead?

"Oh, man." Esposito laid a reassuring hand on his back. "I'm sorry. We'll find the son of a bitch who did this."

" _We_ will," Castle insisted. "Lanie, how'd she die?"

Lanie glanced at Esposito. "Stabbed. She has several knife wounds to the chest and abdomen. Whatever weapon the killer used, it had a wide blade."

"She has a knife block, but no butcher's knife. Maybe that? A weapon of opportunity?"

Lanie shrugged and stood, then removed her gloves. "Could be. You find it, I can match it. Hey." She grabbed Castle's arm when he turned away and pulled him into a hug. "I'm sorry."

"Thanks." Castle pulled away and dialed Kate. "Let's just find the killer."


	2. Chapter 2

The homicide floor of the 12th Precinct was a busy place, detectives and officers alike greeting Castle when he stepped off the elevator before returning to their hushed conversations. The news of the victim's connection to him had spread quickly. Alexis was loved by everyone in homicide, and many offered Castle their condolences and asked him to pass them on to his daughter.

He spotted Kate in an instant. She was at the murder board, Paige's DMV photo already displayed, an almost empty timeline below. The only thing at the moment was the time of death; the neighbor hadn't known the exact time she'd gotten home, but it had been a little after nine in the morning.

Kate turned when he approached, and she grabbed his hand, pulled him into her office. "I'm so sorry," she said, shutting the door before turning to wrap her arms around his neck.. "Have you talked to Alexis yet?"

Castle sighed, his face buried in his wife's neck. His mind had raced nonstop on the drive from Paige's apartment to the precinct, but the feeling of Kate's arms around him and the subtle scent of her cherry shampoo grounded him, eased the dizzying rush of thoughts. "No, she didn't pick up. She's probably in class."

Kate pressed a kiss to the side of his neck and pulled away, fingers threading through the hair at his nape. "Are you okay?"

He lifted one shoulder. "I will be when we find the guilty bastard."

"About that." Kate sighed, then led him to sit on her couch, fingers lacing with his as she dropped onto the cushion next to him. "I know how you're going to react, but I have to say this. You shouldn't work the case, Rick. You're too-"

"Close?" Castle interrupted. He'd expected her to say that. "Like hell I shouldn't work it. I've known Paige since she was a little girl. She's Alexis's best friend. Was," he corrected himself. "I'm working it, Kate. You, of all people, should understand that."

Kate nodded and dropped her eyes to their hands clasped together on her lap. "I know, I'm sorry. I had to." She let go of his hand to brush her fingertips along his jaw. "Whatever you need, okay?"

Castle gave her a small smile. He leaned forward to catch her lips with his, to draw further reassurance from the soft touch. "Thank you. I love you, Kate."

"I love you, too. Keep me posted, okay? I'll help however I can. And Rick," she added when he stood, "be careful."

* * *

"Yeah, if you could send it right over. Thanks." Ryan hung up the phone when Castle emerged from Beckett's office and joined him at the murder board. "I just got off the phone with Columbia. They're sending over her schedule. Apparently, she was a TA for one of her professors. Espo's talking to him now."

Castle took a marker from Ryan's desk and added what he knew to the board. He hadn't seen Paige in several months, so he'd have to get some information from Alexis and Paige's parents.

 _Oh,_ her parents.

"Has her family been informed?" he asked.

Ryan jerked his head towards Beckett's closed door. "Beckett's trying to get a hold of them. Apparently, they're out of the country." He paused. "You alright, Castle?"

"Yeah." He finished writing Paige's major and turned to find Ryan, his brows furrowed with worry. "I'll be better once we solve this."

Esposito hung up the phone and stood, grabbing his coat and notepad. "That was the professor. He couldn't think of anyone Paige had a beef with, except one, who got upset at a bad grade."

Ryan shrugged. "Students get pissed at bad grades all the time, especially at an Ivy League school. What's so special about this one?"

Esposito glanced at his notebook. "Because this one called her, and I quote, 'a lying bitch who deserves everything bad that happens to her.'"

Ryan nodded at the new information, grabbed his coat. "Let's go. You coming, Castle?"

"Yeah." He followed them to the elevator, but his phone rang just as the doors opened. He looked at the screen to see Alexis's smiling face, his heart sinking at the image. "Never mind," he told the boys, turning towards the break room. He shut the break room door behind him before swiping to answer the call. "Hey, Pumpkin."

"Dad? What's wrong? Are you okay?"

Alexis sounded confused, and Castle didn't blame her. His message had been vague on purpose. He closed his eyes, hating that he had to tell his daughter that her life was forever changed. "I'm fine. But, uh, I need to talk to you about something. Where are you?"

* * *

Ryan and Esposito visited the potential suspect's dorm first, only to find out that he was probably in the main library. His roommate hadn't known Paige, or what had apparently happened.

The boys searched the library floor by floor, moving through the stacks quietly, but didn't find the suspect until they reached a study room on the third floor. Esposito motioned for Ryan to flank from the far side, and he approached quietly. "Steven Walker?"

Steven lifted his head from the book in front of him, turning to glance at the badge on Esposito's hip. "Can I help you?"

"Detective Esposito, NYPD. I need to ask you a few - hey!" he yelled when the young man bolted out of his chair, rushing through the library, darting between shelves of books. Espo cursed under his breath as he and Ryan pursued him, ignoring the protests from staff members and other students.

He burst out the front door only to see Ryan with the suspect in front of him, slapping handcuffs on his wrists.

Ryan grinned at his partner. "Been slacking on the exercise?"

Espo just shook his head and tried to catch his breath from the sprint down the stairs. "Shut up, man. Steven Walker, you're coming with us."

Walker was silent for the entire ride to the precinct, speaking for the first time to ask what they wanted when they put him in interrogation. Ryan and Esposito let him stew while they got an update from Beckett about the case and Paige's connection to the suspect. They had no physical evidence, only circumstantial, and not nearly enough to get a warrant to search his room.

They needed a confession.

"Steven Christopher Walker," Ryan boomed as he and Esposito dropped to their seats across from the suspect. "How do you know Paige Galloway?"

Walker looked between the two detectives. "What?"

Esposito leaned forward. "Why'd you run, Steven? Guilty people run. You guilty?"

"Whoa, hold on," Walker interrupted, holding his cuffed hands in front of him. "What's going on? Don't you need to read me my rights? Let me get a lawyer?"

"Why, do you need one?"

"Just tell us about your relationship with Paige," Ryan insisted. He leaned forward as well, mirroring his partner's pose.

"Look, whatever she said about me, it isn't true."

"What isn't true?"

"How do you know her, Steven?" asked Espo, voice raising with simmering anger.

"She's the TA in one of my classes," Steven explained. "She was, ah, helping me with my grade."

Esposito raised an eyebrow. "Then why'd you kill her?"

"I - what?" Steven just stared, eyes wide and glued to the crime scene pictures they laid out before him. His jaw dropped. "I didn't - you think this was me? I didn't do this!"

Ryan set a hand on Esposito's shoulder when he started to stand. "Why'd you run at the library?"

"I thought-" Steven sighed. "I had weed in my bag, man. I thought that's why you were coming after me."

Ryan shared a look with Esposito. "We don't care about the weed. Tell us about Paige."

"She's the TA in my Intro to Psych class. I was falling behind, and she offered to help, get my grade up. I had a paper due, and she claimed I'd plagiarized it, but she wouldn't tell anyone if I started sleeping with her." He dropped his forehead to his hands. "I did, but she gave me a C. I can't get a C, I have a scholarship."

He looked back up at the detectives, panic and worry in his eyes. "Look, man, I was pissed. I found her in the professor's office this morning and confronted her, sure."

"You said she deserved anything that happened to her," Ryan cut in.

"Yeah, but I meant a bad grade or something. We fought, she said too bad about my grade, I left. Went to the library, and I was there until you found me."

Ryan stood and nudged Esposito's arm. "Right, we'll see about that."

"Wait, hang on, one more thing," Steven called out as they opened the door. "I heard her on the phone when I got there. She said she'd see the Dean at 10 tomorrow morning. Maybe whatever that meeting was about got her killed."

"Right." Ryan followed Esposito to the murder board, where Beckett was already adding Steven's testimony. "I'll call the school, get surveillance."

"Make sure you ask about cameras inside the library," Beckett piped up. "I left a message for Paige's building manager for footage from the camera at the main door. If Walker's lying, we'll find out."

"We'll find out if he's telling the truth, too." Ryan pulled out his phone and typed out a text to Castle.

 _Suspect claims Paige blackmailed him after framing him for plagiarism. Can you see if Alexis knows anything?_

Castle's response was immediate. _On it._


	3. Chapter 3

Castle hated this.

He hated seeing his daughter hurt, having her cry on his shoulder as she clutched at his shirt like she would when she was a little girl. Hated that he'd had to tell her that her best friend was dead.

He just held her, arms around her as she sobbed. She had questions, too many that he didn't have the answer to, but he also had questions for her.

Ryan had given him the details of their suspect's testimony, but pending surveillance, they had no idea if he was telling the truth or not. Castle had agreed to see what Alexis knew, if anything.

"Do we know who did it?" Alexis asked after several minutes of silence. She sat up and wiped her tears, smearing them across her cheeks. "Any suspects?"

Castle swept his hand across her back, a feeble attempt to comfort her. "One so far," he admitted. "A student in the class she TA'ed." He was interrupted by his phone buzzing on the table, and he winced when he checked the message. It was from Espo.

 _Suspect alibied out. Cameras at the library confirmed his whereabouts._

Castle sighed. "Well, we _had_ a suspect, but he apparently has a solid alibi. I know this is hard, but do you know anyone else who may have had a grudge against her? Former friends? Rivals? An ex-boyfriend, maybe?"

Alexis sat up. "Yeah, actually. She dumped her boyfriend about a week ago, said she needed to focus on school. I saw him the other day and he was still really upset."

"Good." Castle nodded, bringing up Beckett's contact page. Before he could press the call button, though, there was a knock on the door. He furrowed his brows and glanced at Alexis. "Are you expecting someone?" When she shook her head he stood, the hairs prickling on the back of his neck. "Wait here."

He had to do a double-take when he looked through the peephole and opened the door. "Kate?"

"Hey, Castle," she said, stepping into the apartment. She shoved her hands in her pockets. "Alexis. I'm sorry about Paige."

"Thanks, Kate." Alexis stood and joined her dad. "What's going on?"

Castle studied his wife. She looked nervous, less like the confident captain he knew her to be and far more like someone who was dreading the words that had to come out of her mouth. "We've had a couple things come up. Would you be willing to come down to the station, answer some questions? Help with the timeline?"

"Yeah, of course, anything you need." Alexis grabbed her coat.

Castle took Kate's elbow before she could follow Alexis out. "What's going on?"

Kate sighed. "It could be nothing. I hope it's nothing."

"Kate-"

"We just need some context for a phone call that Paige made, that's all."

"What phone call?" When Kate refused to meet his eyes, he took her hand. "Kate. What phone call?"

* * *

They sat in the break room, Castle next to Alexis, and Kate across from them. She had a folder in front of her, and Castle recognized the look on his wife's face. She'd filled him in on the basics, but without hearing the whole story, he didn't know what to think. He'd been tempted to call his lawyer, but it would work out. It had to.

"How well did you know Paige?" Kate asked first, her voice soft.

Alexis was leaning forward, elbows on the table, her eyes glued to the closed folder. "She was my best friend. We knew almost everything about each other."

"You were both majoring in Psychology." Kate opened the folder and studied part of its contents. "Did you have the same classes?"

"Some, yeah. She was focused more on research, me on criminal psychology." Alexis paused, then looked up at Kate, questions written all over her face. "What's going on, Kate? I thought you needed help on the timeline and info about her ex."

"Yeah, about that." Kate pulled out another piece of paper. "About a week ago, your texts to each other decreased dramatically. Did something happen?"

Alexis hesitated before answering. "We've been focused on school. She'd been struggling so far, but that happens. She was working hard to get back into the swing of things."

"Alexis."

Castle just sat and listened. He had no idea where this was going. Kate hadn't filled him in on everything, which he knew had probably been a good idea.

"Why did Paige call the Dean's office?"

Alexis's head snapped up. "What?"

"Yesterday morning, about an hour before she was killed. She called the Dean's office, left a message that she, and I quote, 'needed to speak to someone about Alexis Castle.' Please, Alexis." Kate leaned forward, her face softening. "What happened?"

"I didn't think she'd go through with it," Alexis mumbled.

"Go through with what?" Castle interrupted.

Alexis shot a look towards him, one that asked for both his help and his forgiveness. "The past year has been rough on Paige. Her parents were having trouble, her grades have been slipping, she got dumped. She'd been having a hard time with one class in particular, so I offered my help, since I'm taking it too. I figured we could share notes and I could help her study."

"And by study-"

"I meant quiz each other and the like. She meant cheat." Alexis finished Kate's sentence with a heavy sigh. "Anyway, we fought about it a couple days ago, again. She wanted me to help her cheat, I said no way. She claimed she just hadn't had time to study. I said she-"

Alexis stopped herself and dropped her head to her hands. "I said she should have thought about that before screwing a student for a grade she didn't even give. She got mad and threatened to call the Dean, and tell him that _I_ had asked _her_ to cheat."

"Alexis-" Castle whispered. He spared a glance at his wife; to the casual viewer she was listening intently, but he could see the worry in her eyes, the tension around her mouth. She knew something.

"That was two days ago. What happened this morning?"

"She texted me, said she was calling the Dean. I told her to go ahead. I didn't think she'd do it." Alexis looked up at her dad, tears shimmering in her eyes. "We've fought before and we've always made up. So I said fine, do it, we'll see what happens. That was when I met you for coffee, Dad."

"She's who you were texting when I sat down."

Alexis nodded. "And that was it. You can check my phone."

Kate audibly swallowed, her eyes on the file in front of her. "I hate to ask you this. But where were you between nine and nine-thirty this morning?"

"I-" Alexis hesitated.

Castle did the math in his head; they'd met at eight, Alexis had left after just a few minutes, and he'd gotten the body call around 9:45. It was a short time of death window.

After a long silence, Alexis spoke again, her voice soft. "I was home. Alone."

The three sat in silence for a few moments until they were interrupted by a quiet knock on the door. Kate stepped outside the room and picked up the phone at Ryan's desk; by the way her shoulders stiffened, Castle knew something was wrong. She returned to the room with a young uniform in tow.

"That was CSU. Your fingerprints were all over Paige's apartment, including the outside of her door. I know it'll be cleared up soon and we'll find who really did it. But for now, can you stick around? At least until I can figure it out."

"Of course my prints are there!"

"Kate-"

"Call the lawyer, Castle." Kate motioned for the officer to step closer, then turned back to Alexis. "Look, just hang out for a while, ok? We'll get this cleared up ASAP." She pulled Alexis into a tight hug. "I'm so sorry about Paige."

"Thanks." Alexis sat back down and raked her fingers through her hair.

"Hang on, you don't actually think she had anything to do with it?" Castle protested, blocking Kate from the door. "Kate, there's no way."

"It's just temporary, Castle. Alexis, can I get you anything?" Alexis just shook her head, and Kate opened the door. "Let me know if you do."

"Just hang tight, Pumpkin." Castle squeezed her shoulders, holding her tight, not wanting to let go until he absolutely had to. They'd figure out what happened, who really killed Paige, and they'd do it soon.

They had to.


	4. Chapter 4

"Thanks, Henry. I'll see you soon." Castle hung up his phone and continued pacing while Beckett finished up a call of her own. He was trying to figure out with whom she'd been speaking. She'd gone straight to her office after their conversation with Alexis, while he'd accompanied his daughter to the conference room. Kate had already been on the phone when he'd rejoined her in her office.

An exasperated sigh from Kate interrupted his thoughts, and he stopped pacing long enough to watch her slam her phone onto its cradle. Obviously, the call hadn't gone as hoped.

She walked around the desk to stand in front of him and took his hands, tried to pull him into her arms. She stumbled back when he pulled away. He didn't want a hug, couldn't stand the comfort, the pity. He wanted his daughter free from suspicion.

"She's innocent, Kate," he insisted, raking his fingers through his hair. "Motive and lack of alibi be damned. Of course her prints were there, she was Paige's best friend." He swore under his breath and collapsed onto the couch.

"Hey." Kate joined him on the couch. "I know, Rick. Look, you know I'll do whatever I can, call in every favor I have if I need to. But I've talked to the DA twice now, and I have no idea how he got wind of it, but he's gearing up for this case."

Castle scoffed. "Isn't he up for re-election?"

"Yeah, and I'm sure he doesn't want it to seem like he'll let people go because they're rich. Not to mention, the Twelve is under a bit more scrutiny because of the LokSat stuff last year." Kate took his hand and laced her fingers with his. "He wants Alexis arrested, and the case moved to another precinct. I convinced him to hold off on any arrest warrant, but he's on his way right now to personally oversee the transfer of the evidence we've collected."

"Please, Kate, she can't," Castle pleaded. "Let Ryan and Espo keep working it."

"Oh, they are. I'll delay the DA as long as I can, and they have no intention of standing by while there's a killer to be caught and a Castle to be exonerated." She squeezed his hand and waited for him to meet her eyes. "Everyone here loves Alexis. She's family. She'll be out in no time."

"Thanks, Kate." Castle sighed and wrapped his arm around her shoulders, pulled her into his side. He felt completely helpless, but Kate would do everything in-and out-of her power to clear Alexis's name to find the real killer. "Hayley's on her way too," he added. "This is her only case right now."

* * *

"Do you think there's a chance they'll press charges?" Alexis asked in the conference room, sitting next to her dad, across from the two lawyers he'd called in.

Henry Browning glanced at his partner, criminal defense attorney Lance Hagan. "Doubtful. Their evidence is all circumstantial, and they haven't looked at anyone else since focusing on you."

"It is concerning that the DA's already involved," Hagan admitted. "Like it or not, your father is rich, and he wouldn't hesitate to pay anything to get you out if you were arrested. There's a good faction of voters who don't like that, and it is an election year."

"So, they could press charges. I could actually go to jail for this? But I didn't do it!"

"We know, Alexis. Just hang tight, okay? Without a murder weapon, they really don't have anything."

Alexis hung her head in her hands after her dad and lawyers left. She'd been around cops, and Kate, enough to know that, even though she was innocent, the justice served was often wrong. Kate had told her stories of innocent people being put away, and guilty ones set free. Hell, it had happened with Kate's own mom. That justice took fourteen years to be served.

"It'll be okay."

Alexis looked up at the unfamiliar voice to see Officer Hernandez. He must have been new; she didn't remember seeing him before. All she could think to respond with was "What?"

Hernandez gave her a sheepish smile. "Sorry. I shouldn't say anything, it's not my place. But even if they do press charges, they won't stick." He shrugged. "As far as I can tell, the evidence is circumstantial."

Alexis blinked at him. "Why are you telling me this?"

"I don't like seeing people unjustly prosecuted. And I've seen you around, I know who you are. There's no way in hell you did this."

* * *

Hayley went straight into Kate's office upon arrival and shut the door behind her. "Okay, fill me in. What happened?"

"Alexis's best friend was killed," Kate started. She explained the whole case, from the crime scene to the initial suspect who'd alibied out, to the DA's desire to arrest Alexis.

Hayley was silent throughout, interjecting with questions when necessary, but for the most part just listened. "Okay, has anyone spoken to the ex?" she asked first.

Ryan shook his head. "No, we were ordered off the case before we could. We don't even have access to his information anymore."

"Okay, well, give me the name, I'll go talk to him."

She was at the ex-boyfriend's apartment shortly after, pounding on the door. "Mark Darnell?" she asked when the door opened. At his nod, she continued. "Hayley Shipton, private investigator. I need to ask you a few questions about your ex." She pushed her way past him, stopping just inside the door.

Mark pushed back the hood of his dark sweatshirt. "What about her?"

"I understand you recently broke up."

"Yeah, so? What'd the bitch say about me?"

Hayley's eyebrows shot up. "That bitch, huh? What _would_ she say about you?"

"I don't know, but whatever it is, it's a lie. _She_ dumped _me._ She was a cheating, lying bitch, but she beat me to it, claimed she needed 'more time to study.'" He punctuated his statement with air quotes.

Hayley crossed her arms over her chest. "So, is that why you killed her?"

"Wait, what?" Mark's jaw dropped. "No, I didn't - she's dead?" His eyes widened and he leaned on the arm of the couch. "Damn. And you're - you think I had something to do with it?"

Hayley shrugged. "You just told me you were pissed about her breaking up with you."

"No, that's not-" Mark sighed and rubbed a hand over his face. "Damn. Okay, let me explain."

"I think that's a good idea."

"We'd been dating, oh, almost a year. So last week, she breaks up with me, says she needs to focus on her studies. Thing is, I didn't believe her. I'd seen her hanging around this sophomore, or with her professor. She kept going on about how broke she was, too, but she kept buying stuff. Always had new clothes, stuff like that."

Hayley nodded, silent until he finished his story, making mental notes to point out to Ryan and Esposito. "Alright, so, where were you this morning?"

Mark didn't hesitate. "Hung over at a friend's place. He had a party last night, I crashed there, didn't get home 'til noon. You can ask him and his girlfriend, she made breakfast."

"I'm going to need their names."

* * *

Hayley met Ryan and Esposito at the PI office. They'd managed to sneak Paige's financial records from the evidence box, and divided them amongst themselves. After just a few minutes Esposito pointed out a series of deposits: every couple of months over the previous year, she'd made cash deposits of $5,000. They most likely weren't from her parents, any deposits from them had been electronic.

While the guys reviewed Paige's financials, Hayley looked into the professor that Paige had TA'ed for. Professor Robert Birch, 47 years old, on track for tenure. She had Ryan call the Psychology department head for more information; while Birch was on the tenure track, he was also in danger of not getting it. He'd been trying to get published.

Ryan called the Dean next. If Birch didn't get published, he wouldn't get tenure, and he'd lose his job.

"Do you know why he can't get published?" Ryan asked, the phone on speaker.

They heard a sigh. "There have been reports of suspicious behavior over the past few years," he admitted after a long silence. "I don't have any proof, but there are rumors that he might have been plagiarizing some of his work. I've been keeping an eye on him, but he's careful. I haven't been able to catch him."

Hayley shared a look with Ryan and Esposito. They needed to find the professor.


	5. Chapter 5

Castle and Alexis sat in silence, Alexis staring past him as she took in his latest update on the case. Her dad had filled her in, told her about the suspicion on the professor. She'd never had Professor Birch as a teacher, but the story was finally starting to make sense.

"I'm sorry, Dad," she said to break the silence.

"For what?"

She sighed, her gaze falling to the floor. "For this." She motioned to the room, empty save for the two of them. "If Paige and I hadn't fought, if I'd just listened to her instead of getting mad…"

Castle shook his head, reaching to stop the frustrated movement of her arms with his hand. "No, sweetie, don't go there. You did what you felt was right, refusing to help her cheat. The way she reacted? That's on her."

"Our last conversation was an argument," she pointed out. "How the hell am I supposed to live with that?"

Castle fell silent, his hand tracing a pattern on her arm. "I don't know," he admitted. "Focus on the good memories. Be thankful for the friendship that you had, don't dwell on how it ended. You would have made up if you'd just had more time."

"I guess." Alexis sighed. "The guys are going to get in trouble, aren't they?"

"What do you mean?"

"Kate told me they're working on it, even though they shouldn't be."

"It's fine." Castle smirked. "Technically, they hired Hayley at a family and friends discount of one hundred percent. She's in turn using them as consultants for the same, non-existent fee."

Alexis and her dad shared a chuckle at the complicated cover story, the sound of her laughter easing some of the pressure in his chest. "It'll be okay, right?"

Castle sighed. "Remember a few years ago, when I was framed by Jerry Tyson?" When Alexis nodded against his shoulder, he continued. "If we could get through that, through you being kidnapped and taken to Paris, all the rest we've been through together? Proving your innocence will be a piece of cake."

"I hope you're right."

"Hey, guys."

"Kate." Castle stood at the sound of her voice. "Anything new?"

Kate joined them at the table. "I just talked to Hayley. She's tracking down the professor right now, and I'm considering him a suspect." She reached out and covered Alexis's hand with hers. "I won't stop, Alexis. No matter what."

Alexis gave Kate a small smile. "I know. Dad, can you give us a minute?"

"We'll find whoever did this," Kate started once Castle was down the hall.

"Kate." Alexis interrupted with a hand on her shoulder. "I know. I'm grateful for you putting your neck out for me."

"You're family, Alexis. I'll do anything for the people I love."

She let that sink in, and after a few long moments, Alexis spoke again. "Can you do me a favor?"

"Anything."

"If something happens, you'll take care of Dad, right? I wouldn't want him...he has Gram, but…" She looked up at Kate, her eyes wide and innocent, brimming with unshed tears. "Please?"

Kate drew Alexis into her arms, feeling the younger woman sink into the embrace with a quiet sigh. "Of course. I'm not going anywhere." She squeezed Alexis's shoulders. "We'll get through this, I promise."

* * *

Ryan knocked on Professor Birch's door, relenting only after several minutes of pounding without a response.

"Allow me," Hayley offered, nudging him to the side. She pulled a kit from her coat pocket, selected the right lock picking tools, and went to work on the deadbolt.

"What are you doing?" Ryan asked, sneaking a glance at where Espo was standing guard down the hall.

Hayley bit her bottom lip in concentration. "Just being - ha!" she exclaimed when the lock gave away. She turned the knob and opened the newly unlocked door. "Just being creative. Make sure not to touch anything, yeah? This isn't exactly legal."

Espo scoffed. "You don't say." He handed Hayley a pair of gloves.

They split up when they entered the sparse apartment, Ryan and Espo clearing it first. Hayley searched the kitchen; they were searching for anything to point to motive, although they wouldn't complain if they found the murder weapon. Granted, they'd have to figure out a way to search the apartment legally, but…

"Yo, I found something," Espo called out from the bedroom. Hayley and Ryan joined him to find him holding a messenger bag in one hand and a butcher knife with something that looked like dried blood in the other.

"There's just one problem, guys," Hayley pointed out. "We can't use it."

" _We_ can't," Esposito said, motioning to himself and Ryan, "but _you_ can."

Hayley crossed her arms over her chest. "And what's that supposed to mean? I broke in here. You're cops, you could lose your jobs just for being here, let alone unlawful seizure if we take it. We need something that will get a warrant, not-" She was interrupted by Ryan's phone.

Ryan glanced at the screen before answering. "It's Beckett. Hey, Cap," he said, the phone on speaker.

"Hey, are you with Espo?"

"Yeah, why?"

Beckett sighed. "I need you back here. And, fair warning," she added, her voice dropping, "the DA is here, and he is _pissed._ "

* * *

Beckett hadn't been kidding when she said the DA was angry. He was pacing in her office when Ryan and Espo returned to the precinct, but to Beckett's credit she was standing her ground, arms crossed, defiance written all over her face.

Beckett walked out of her office when she spotted Ryan and Esposito, and she must have left the DA mid-sentence, because he looked ready to explode. She just smirked when she approached the boys. "Good job, guys."

They followed her to the break room. "We found the knife," Espo started as soon as the door was shut.

Beckett did a double take. "Okay, back up. Where?"

"The professor, the one she TA'ed for? He's shady. Accusations of plagiarism, could be losing his job at the end of the year. Hayley went back to the PI office to try and get financials, see if we can trace those deposits Paige had been getting."

"And the murder weapon?"

Ryan hesitated. "Well, we kinda broke into his apartment. The good news is, we found it. Bad news-"

"It was illegally obtained. Tell me it's still there and you have a plan."

"Yeah."

"Okay." Beckett nodded, her eyes wandering back to the bullpen, where the DA was rifling through the evidence box. "You guys keep doing what you're doing," she instructed, smirking. "He's pissed because Paige's financials are missing. It would be a shame if he couldn't get an arrest warrant because of insufficient evidence."

The three of them shared a look, and Kate stepped to the coffee pot. "I'll keep delaying him," she offered, filling two mugs. "Find Robert Birch. I'll figure out a way to get a search warrant for the apartment."

* * *

Hayley was back at the PI office, fingers flying over her keyboard as she traced Birch's cell and pulled his financial records. She'd noted the dates of Paige's deposits, and as soon as she got what she needed, she was confident she'd find the corresponding withdrawals on his statements. She was also hoping to recover any text messages exchanged between the two, _anything_ to prove his guilt and clear Alexis's name.

The financial statements came back first, and she scanned them, a triumphant cry when she found the withdrawals she was looking for. "Hey Ryan," she said when he picked up his phone. "I found something. Birch was paying off Paige, he had to be. And you'll love this: he took out five thousand dollars yesterday, then redeposited it just an hour ago."

"That must have been where he was when we stopped by," Ryan mentioned. "Great, Hayley, thanks."

"No problem." She was about to hang up when her second search beeped. "Oh, hey, Ryan?"

"Yeah?"

"I found him."

* * *

Castle was just going up the steps to the precinct when his phone rang. He hadn't wanted to leave, didn't want to be away from Alexis. But Kate had sent him to get food.

He figured it was partly to get him out, based on the pointedness of her stare as she'd asked; his pacing in the break room and her office probably got on her nerves. He couldn't help it though. When it came to the people he loved he was a man of action, whether it was going after Jerry Tyson to find Kate, or flying to Paris to rescue his kidnapped daughter.

So the last thing he wanted to do was sit on his ass or, even worse, watch the DA take Alexis out of Kate's precinct. She was innocent, and he knew it, the whole team knew it, but they just needed to prove it. And while he had every confidence in Hayley and the boys, Alexis was his daughter, and he felt helpless.

He hated feeling helpless.

Hayley's name on his screen made him step to the side, the initial dread that hung heavy in the pit of his stomach slowly dissipating. "Hayley," he greeted her, slightly out of breath from nerves and his walk. "What's up?"

"It was Paige's professor."

Castle froze. "What?"

"He has the murder weapon, Rick. But I found it illegally, so I need Alexis's help."

Castle went straight to Kate's office, where the food went ignored in favor of taking the DA to see Alexis.

"Ex-boyfriend aside," Kate argued before they went to the conference room, "you've been so focused on Alexis this whole damn time that we haven't been able to even _look_ at anyone else."

"Like hell you haven't," District Attorney Scott Foote said. "Don't think I haven't noticed that Detectives Ryan and Esposito have been MIA today, or that those financials still haven't been found." He stopped outside the room. "You've been stalling all day, Captain. What are your detectives up to?"

Kate just folded her arms over her chest and glared at him. "They're trying to keep an innocent woman out of jail."

"A young woman who happens to be your step-daughter."

"What's your point?"

"My point is, you're on a tight leash, Captain. When this is all over, I'll be watching you like a hawk."

"And I'll be supporting your resignation," Kate shot back. She gave Alexis a small smile when the three of them crossed the threshold. "Hey, how are you holding up?"

Alexis shrugged. "I'm okay. What's up?"

"We talked to the ex-boyfriend," Kate started, sitting next to her. "He said Paige had been spending a lot of time with Professor Birch, and she'd seemed to have more money than she should. Do you know anything about that?"

"Um, she said once that if she ever needed a favor, Professor Birch would be the one to go to." Alexis paused. "I did notice the money, like she didn't seem to have trouble paying rent. But her parents are rich, so I assumed they were helping her. We didn't talk about money very much."

Kate glanced up to where the DA was leaning against the wall, arms crossed. "Do you know what she meant about Birch? Did she do a favor for him? Why would he owe her any favor?"

Alexis shook her head, eyes down. "I have no idea, but she was cocky about it. Like, 'I can do whatever I want, Birch would bail me out.'"

Castle scoffed from his perch on the other end of the table, but when Kate threw him a look, he bit his tongue. "Whatever it was, it's worth talking to him," he did say, managing to keep his voice steady. Pissing off the DA wouldn't help matters at all.

"You know as well as I do," Kate continued, fixing a glare on the DA, "that our _very_ good lawyers will exploit the fact that you blatantly ignored legitimate suspects for an innocent, upstanding young woman who happens to have a rich father."

Foote returned Beckett's glare, but after a few long moments, sighed in exasperation. "Fine. Have someone talk to the professor." He turned to leave, but hesitated, and turned back. "Not Detective Ryan or Detective Esposito."


	6. Chapter 6

It wasn't easy in the waning hours of the evening, but Hayley managed to spot the professor as he left his building. She'd been watching the apartment since she'd traced his phone there, and had called the boys when it had seemed like he'd be staying for awhile. They had questioned him with Hayley listening on speakerphone, but he revealed no answers.

The plan had been simple: the boys would talk to Birch, pretend they didn't know anything about his relationship with Paige. But over the course of the twenty-minute conversation, they steered it to how Paige had been killed or any potential motives. Eventually, Birch had clammed up and had all but forced the detectives to leave.

So they'd kept on the apartment since, just watching, waiting.

Birch stepped onto the sidewalk, gaze darting across his surroundings and presumably searching for anyone watching him, before he took a right turn. He obviously didn't notice Hayley, because he walked down the sidewalk at a fast clip.

Hayley sent a short text to Espo to let him know she was on the move; the boys were covering the back and side of the building. She kept several steps behind Birch as he turned one corner, then another, consistently letting the boys know where she was going.

The evening crowd was starting to thin, so Hayley had to be more careful, but as she turned yet another corner, she froze when she saw Birch step into an alley. Before she could sneak to the alley entrance, though, a swarm of police cars pulled up, sirens blazing, trapping Birch in the alley.

Hayley watched with a smile as Birch was arrested and placed in the back of a police car.

* * *

Beckett didn't waste any time. She strode into interrogation with confidence and two evidence bags and sat down, eyes on Birch.

She'd seen suspects of all shapes and sizes, had seen more reactions than she could count. But rare was the time she could interrogate someone who she knew was the killer. Even more rare were times when the killer knew they were caught and while she enjoyed the cat-and-mouse game of getting a suspect to confess, she was looking forward to pressing charges against this man.

"Why'd you kill Paige?" Kate asked, not wasting any time.

"I-" When Kate just raised an eyebrow and showed him the bag containing the murder weapon, Birch's shoulders slumped. "I didn't plan it," he admitted.

"Just tell me what happened."

Birch sighed. "I've been trying to get published for years, with no luck. If I don't get tenure I might lose my job, so I got desperate. Started to copy parts of papers, found that other people's words were better than mine. Paige found out last year and threatened to out me. But I couldn't let her, I have a family to support. I thought I could buy enough time to make it work."

He clasped his hands together, fingers playing with his wedding ring. "So, she blackmailed me. My money for her silence. And God help me, I paid her."

"What changed?"

"She got reckless," he said. "She started waving the money around, and her grades started to fall. She even had a fling with one of my students. So, today I went to her apartment to try to get her to stop, because I was afraid I'd be found out. People would start asking questions. We argued, she told me to leave, but I couldn't. I threatened to stop paying her, she said she'd out me."

Kate lifted the bags, one containing the knife, the other a bloodied navy sweatshirt that CSU had found in his laundry hamper. "We matched the knife with the stab wounds in Paige's body," she explained, "and when the DNA comes back it'll be a match with her as well."

"I didn't go there to kill her," Birch muttered. "But she turned away, and I saw the knife. I was just so mad…"

He trailed off, and Kate collected the evidence and opened the door. "It's over, Birch. You're done."

* * *

"Are you serious?" Alexis asked as Kate opened the door. She stood, wiping her hands on her slacks. "Professor Birch really killed her?"

"Yeah. We have the murder weapon, solid evidence, and his confession. You're free to go, no charges."

"Thank you." Alexis gave Kate a tight hug, eyes brimming with tears. "For everything."

Kate squeezed her before giving way to Castle, who practically pushed her aside to get to his daughter. "I'd say anytime, but I don't want any more family members accused of murder."

Alexis couldn't stop the chuckle as she pulled away from her dad. "I'm with you on that."

"You ready to get out of here?"

"Um, give me a sec?" She waited until Kate led her dad away, a knowing smirk on her face, and walked up to Officer Hernandez. He'd been on duty the entire afternoon, had made the time she'd been alone bearable. "Thanks, Officer."

"Kyle," he interrupted, accepting Alexis's outstretched hand. "It was my pleasure. I'm sure I'll see you around."

Alexis grinned. "Yeah, I'm sure you will." She hesitated before giving him another nod and turning away. "See you later, Kyle."

She found Ryan and Esposito in the bullpen, closing up the evidence box. The murder board was empty, presumably taken down when the DA had tried to have the case transferred. Both of the detectives greeted her with hugs, expressed their gratitude that she was okay, and most importantly, free.

"I know you guys took a huge risk by helping me," she said, "and I am so, so grateful for that. Thank you."

Ryan lifted a shoulder in a shrug. "It was nothing, Alexis. It's what we do for family."

* * *

Kate sighed as she and Rick walked through the door, and she used his shoulder as leverage to take off her heels. She was exhausted; all she wanted to do was collapse on the couch with a glass of wine and curl up next to her husband. The curling up she could do, but she dropped her head to his shoulder when she remembered that wine was off the table for the foreseeable future.

"You okay?" Castle asked, his arm curling at her waist, fingers drifting just below her rib cage, his lips at her temple.

Kate nodded against his shoulder. "I want wine," she complained.

Castle chuckled and nudged her head up, cupped her cheeks so he could kiss her softly. "I know. I can make you tea instead?"

"Yes please." She followed him into the kitchen and watched as he retrieved a wine glass, paused, and put it back. "You can have wine, babe. I won't hate you for it."

"It's alright." He put the kettle on, then joined her at the island. "Thank you," he said quietly, reaching over to take her hand and lace their fingers together.

Kate's thumb circled over the skin of his hand. "For what?"

"For what you did today. Being you." He tucked a lock of hair behind her ear, hand lingering at her jaw, and gave her a soft smile. "You'll be a great mom, you know. You already are."

Kate smiled and leaned forward to kiss him, her tongue swiping at his bottom lip. "I love you," she whispered against his mouth when she pulled away.

Castle smiled. "I love you, too."

* * *

Alexis was alone in her apartment, a glass of wine on the coffee table next to a photo album. The album was of her and Paige, pictures from their lifelong friendship. Kate had invited her over, but she'd just wanted to go home. Her dad would have been all over her, almost suffocating, and she needed space.

She swiped at her cheeks when there was a knock on the door, rushing over to answer it, and was surprised to see Hayley through the peephole. She sighed before opening it. "What's going on?"

Hayley lifted the pizza and beer in her hands. "Thought you might want some company."

"I appreciate it, but honestly, I'd rather be alone." Alexis wiped fresh tears from her cheeks, then stepped aside to let Hayley in. "No, I don't," she admitted.

Hayley joined her on the couch after grabbing plates and a bottle opener. "Aw, look at you two!" she said with a smile, pointing at a picture of a young Alexis and Paige.

Alexis chuckled through her tears, her fingers touching the edges of the picture. "We were eight," she explained, the memories of her friendship overwhelming her. "We begged Dad to take us ice skating, but the rink was closed and we didn't want to deal with Rockefeller. Instead, we went to Central Park and had a snowball fight, Paige and me against him. We killed him, of course-" She froze at her choice of words.

"I can't believe she's gone," she admitted, shaking her head. "I'll never see her again. Never get another text, or phone call, run into her in the library…"

Hayley rested her hand on Alexis's back. "You know, I've lost a few friends. And one thing I've learned is that if you focus on the good memories rather than the bad, it will start to hurt less."

Alexis nodded. "Thanks, Hayley."

"Anytime." She paused, allowed Alexis a moment to quell the sadness before speaking again. "Now, I _have_ to know about this picture. Please tell me you're wearing that because it was Halloween."

* * *

 _Episode beta work by ivyandtwines and amtepe_

 _Castle Season 9 is produced by Team Planet and the writing team of Castle Season 9_ _. Executive Producer is_ _encantadaa._

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